1. Field of the Invention
The present invention relates to a levitating and fusing device in which an object to be heated such as metal or the like is inserted into a crucible composed of a plurality of segments, each of which is formed of a conductive material, and disposed inside an induction coil, and the object to be heated is floated and is then fused in the levitating state thereof.
2. Description of the Prior Art
The metal that is fused according to a levitating and fusing method of the above-mentioned type is free from impurities contained in the crucible and, therefore, it can provide a fusion of high purity. Accordingly, by pouring the fused metal into a mold, a product of high quality can be manufactured. For example, the levitating and fusing method is applied to fuse titanium, silicone and the like.
In FIG. 13, there is shown a plan view of a conventional crucible and, in FIG. 14, there is shown a partially sectional perspective view of the crucible shown in FIG. 13 and having coils mounted thereto. In these figures, according to a conventional levitating and fusing device, there are arranged inside circular induction coils 1 a plurality of segments 2 each formed of an electrically insulated conductive material such as copper and the like in the peripheral direction of the induction coils 1 to thereby construct a crucible 3. The inside of the crucible 3 is hollowed out to provide a cylinder with a bottom, into which cylindrical crucible 3 is inserted an object to be heated such as metal and the like. Also, in the center portion of the bottom of the crucible 3, there is opened up a small cylindrical hole 4. A magnetic flux is allowed to enter the crucible 3 from the hole 4 and slits 5 interposed between the adjacent segments 2 and is then interlinked with the object to be heated. The segments 2 are cooled by water or the like so that they cannot be heated.
A current flowing in the induction coils 1 induces an eddy current in each of the electrically insulated segments 2 and it also induces an eddy current in the object to be heated. Not only in the case where the object to be heated is a non-magnetic metal, but also in the case where it is a magnetic metal since the magnetic metal becomes a non-magnetic metal when it is heated up to a temperature equal to or higher than the Curie point, the directions of the eddy currents respectively flowing in the crucible 3 and the object to be heated are mutually opposite to each other in the opposing surface portions thereof and, therefore, there is generated a magnetic reaction force between the crucible 3 and the object to be heated. Since the crucible 3 is fixed, if a levitation force acting on the object to be heated is greater than the weight of the object to be heated, then the object to be heated is floated off from the crucible 3. The eddy current flowing in the object to be heated 6 generates heat due to ohmic loss to thereby be able to keep heating, so that the object to be heated can be fused in the levitating state thereof. However, with the conventional levitating and fusing device thus organized, it has been insufficient to float the fused metal with high energy efficiency and in a stable manner.